On a computer, a user can play a game of Go with a computer or another user via a network. Go is a game in which players compete over the size of territory, and it is important that the player establishes a strategy and makes moves while constantly considering how to keep the player's own stones alive and how to kill the opponent's stones in a given situation.
For example, if the player can judge that the player's own stones are dead at an early stage, the player can abandon that territory and concentrate on another location, which is also very efficient as an overall strategy. For this reason, it is extremely important in Go to determine whether one's own stones or the opponent's stones are alive or dead. The question of whether stones are alive or dead is referred to as “life and death.” Living stones are those that cannot be captured by the opponent's moves or that, if captured, produce stones that cannot be captured again by the opponent. Dead stones are those other than living stones and that can be captured by the opponent's moves.
In addition to playing a role in strategy during a game of Go, the life and death of stones must also foe judged at the end of the game. The life or death of stones is also important from this standpoint. For this reason, there also exist sets of problems, called tsumego, for solving localized cases of life and death.
Assessing the life or death of stones is thus extremely important in Go, but actually assessing whether stones are alive or dead is not easy. In particular, computers have difficulty doing so automatically. Accordingly, systems for performing processes associated with the life and death of stones have been disclosed, as in, e.g. the following Patent Documents and Non-Patent Documents.